1620s (trans.), "immerse, plunge into (a fluid)," from Latin immergere "to dip, plunge into" (see immersion). Intransitive sense from 1706. Rare; the usual verb is immerse. Related: Immerged; immerging.
c. 1500, from Late Latin immersionem (nominative immersio), noun of action from past participle stem of immergere "to plunge in, dip into, sink, submerge," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + Latin mergere "plunge, dip" (see merge). Meaning "absorption in some interest or situation" is from 1640s. As a method of teaching a foreign language, 1965, trademarked by the Berlitz company.
"to plunge into (a fluid)," early 15c. (implied in immersed), from Latin immersus, past participle of immergere "to plunge in, dip into, sink, submerge" (see immersion). Figuratively, of study, work, passion, etc., from 1660s. Related: Immersed; immersing; immersive.