In terms, etymology (TR:44) (LH:4) (TL:48), from etymos- meaning “true, real, actual” + -ology meaning “study of, speaking of”, is the study of the true origin of words, terms, and names; a matter of unwrapping or decoding a name to find the message the namegivers have placed inside (Barney, 1998).
In 2500BC, Egyptians developed the model of assigning each person or god with a main name and a secret name; according to which, if one gained knowledge of the secret name, they were said to have power over the person or god.
Gematria | Isopsephy
In 1000BC, Greeks, after studying abroad in Egypt, developed the Greek alphabet, each letter having a coded symbolic meaning, upon which they employed a "number method" to assign a so-called secret name to each word, e.g. the word "theta", the name of 9th letter (Θ) of the Greek alphabet, has an isopsephy value of "318". The Hebrew equivalent of this word number coding technique is called gematria. The number of a word, being it done via isopsephy (Greek word to number) or gematria (Hebrew word to number) is called the word's "numerical equivalent" (NE) value.
The Greek sun god Helios, in secret or hidden connection to the word theta, is a word that also has a gematria value of "318". Hence, Helios is the secret name or hidden meaning behind the term "theta", in the sense of theta being a heat, sun, or sun god themed word. This explains why the character of "Θ" is shaped like a sun, and also why it has a number value of nine, per reason that it is symbolic of the nine gods of the Heliopolis creation myth, the supreme sun god family of Egypt. Subsequently, as the Θ-symbol renders as the sound "Th-" in modern English, one finds that most Th-based are sun or sun god related, e.g. thermometer or theology or thought or think. This is what is called "hidden etymology". The Hebrew variant of this word numbering scheme is called isopso
In the 1640s, etymology as an independent branch of study, within linguistics, began to form. Most of this work amounts to what is called surface etymology or "scratch etymologies", i.e. etymologies that only "scratch the surface" of the true underlying meaning of the word. The majority of modern etymological scholarship, is rooted or based in surface etymology arguments, most amounting to baseless arguments.
A simple example of scratch etymology, can be found in debates over the origin of the letter “N”. Many, in modern times, will bend over backwards to argue that N originated as rearing “snake” symbol, in proto-Sinaitic script (1700BC), owing to one small squiggle mark on a 10-centimeters section of a two-inch mini sphinx found in a Hathor temple, because Alan Gardiner (1916) “says so”. Correctly, the N symbol derives from the water wave ripple symbol, and is symbolic of the Egyptian god Nun. The same is the case with respect to the etymology of the word "chemistry", which for many, ignorant of post post-Rosetta stone reform, simply trace the origin to the Arabic word "kimiya", rendered as "casting together", e.g. al-kimiya (alchemy), and stop there. Correctly, the Arabs derived their sciences by copying and translating the works of the Greeks. The Greeks, in turn, derived their science by copying and translating the works of the Egyptians.
In the 1840s, following the decipherment of the Rosetta stone, some semblance of true etymology began to form. Most attempts at true post-Rosetta stone era etymology, however, is clogged up by the false etymologies of the previous two centuries. Hence, words such as "hour" (12 stages of Horus) or "horizon" (zone of Horus), which related to the god Horus as the sun, the name "Hor" dating to 3200BC, such as the pre-dynastic pharaohs named themselves, as sun gods, e.g. Hedju Hor (3250BC), Ny-Hor (3180BC), or Iry-Hor (3170BC). Likewise, the location and or time where or when the light of the sun apparently disappears at night, aka "sunset", derived from the god Set, who Horus was said to do battle with each night. Hence, "sun set" in the original pre-Greek etymological sense of the word means that the time when the sun begins to do battle with Set. Derived words include "setting" something down, e.g. to "set" a cup down, etc.
The following are quotes:
- “Etymologically, the word ‘neter’ may mean power, or, as some think, nature, but etymology is ever a shifting sand on which to build.”
- — Hunt Cooke (1904), “Review: of On the Gods of Egypt by Wallis Budge” (pg. 376) 
- “As practiced by Socrates in the Cratylus, etymology involves a claim about the underlying semantic content of the name, what it really means or indicates. This content is taken to have been put there by the ancient namegivers: giving an etymology is thus a matter of unwrapping or decoding a name to find the message the namegivers have placed inside.”
- — Rachel Barney (1998). “Socrates Agonistes: the Case of the Cratylus Etymologies” 
- Barnhart, Robert. (1995). Barnhart Concise Dictionary of Etymology: the Origins of American English Words (GB). Harper Collins.
- Etymology – EtymOnline.com.
- N – Hmolpedia 2020.
- Etymology of chemistry – Wikipedia.
- List of Pharaohs (predynastic) – Wikipedia.
- Cooke, Hunt. (1904). “Review: of On the Gods of Egypt by Wallis Budge”, Biblia: a Monthly Journal Devoted to Biblical Archaeology and Oriental Research (editor: Charles Davis) (pgs. 374-80, quote, pg. 376). Biblia.
- Barney, Rachel. (1998). “Socrates Agonistes: the Case of the Cratylus Etymologies” (pg. 64); in Oxford Studies in Ancient Philosophy, Volume 16 (editor: C. Taylor). Publisher.
- Etymology – Hmolpedia 2020.