DRAGON. Two Heb. words תַּנִּים, תַּנִּין, H9490, are tr. “dragon” KJV in all except four passages (see below). Although almost identical these words are thought not to be cognate. (For detailed discussion on these roots see NBD, p. 322.) Tannim (masc. pl. of Tan) and, once, tannoth (fem. pl.) are tr. fourteen times as “dragon” (KJV) and “jackal” (ASV and RSV). In the only other occurrence (Ezek 32:2) it is tr. “whale” (KJV), “dragon” (ASV, RSV). It is tempting to regard this as a textual error for tannin (below), for all the other contexts have enough in common to confirm the ASV and RSV “jackal” (q.v.).

Tannin is less uniformly tr. “dragon” (7), “sea monster” (1), “serpent” (3), “whale” (2) in KJV; “dragon” (6), “sea monster” (2), “serpent” (4), and “jackal” (1) in ASV and RSV. These words are used literally in only two passages: (a) Genesis 1:21 “whale” (KJV), “sea monster” (ASV, RSV); (b) Exodus 7:9, 10, 12, serpent,” all Eng. VSS. All other contexts are fig.: (a) in the Creation narrative, fifth day, and the word is clearly a general one that might be better tr. “giant marine animals”; (b) the incident of the rods that became serpents (q.v.). For the rest the tr. “dragon” is perhaps as good as any, for the use is pictorial and allegorical. There is some logic in allowing the Heb. tannin to have two meanings, mythological and biological, for this is true of Eng. “dragon.” Defined first as a mythological monster with wings and claws, the word is also found in such animal names as komodo dragon (a giant lizard), dragon fish, dragonfly, etc.

The NT position is simpler. Δράκων, occurs only in Revelation 12:13, 16, 20, where it is used fig. for Satan. In LXX, Heb. tannin is usually tr. δράκων, G1532.

International Standard Bible Encyclopedia (1915)

(tannin, plural tannim, tannoth; drakon):

On the constellational dragons or snakes, see Astronomy, sec. II, 1-5.