diving (n.)

c. 1200, diven, "descend or plunge headfirst into water," from a merger of Old English dufan "to dive, duck, sink" (intransitive, class II strong verb; past tense deaf, past participle dofen) and dyfan "to dip, submerge" (weak, transitive), from Proto-Germanic verb *dubijan, from PIE *dheub- "deep, hollow" (see deep (adj.)).

In the merger of verbs the weak forms predominated and the strong inflections were obsolete by 1300. The past tense remained dived into 19c., but in that century dove emerged, perhaps on analogy of drive/drove. The change began to be noted in the late 1850s by Canadian and U.S. editors: Bartlett (1859) notes it as an Americanism, "Very common among seamen and not confined to them," and a paper read before the Canadian Institute in 1857 reports it in Canadian English. All note its use by Longfellow in "Hiawatha" (1855).

From early 13c. as "to make a plunge" in any way; of submarines by 1872; of airplanes by 1908 (hence dive-bombing, dive-bomber, both 1931). Figurative sense of "plunge entirely into something that engrosses the attention" is from 1580s. In Middle English also transitive, "to submerge (something), make to sink down."