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gag [gag 词源字典]: gag: [15] Middle English gaggen meant ‘strangle, suffocate’, so the word started out with strong connotations that seem to have become submerged in local dialects as it came to be used more commonly in the milder sense ‘obstruct someone’s mouth’. In the 20th century, however, they have re-emerged in the intransitive sense ‘choke’. It is not clear how the 19th-century noun sense ‘joke’ is connected, if at all. As for the word’s source, it is generally said to have originated as an imitation of someone retching or choking.
[gag etymology, gag origin, 英语词源]
sink (v.): Old English sincan (intransitive) "become submerged, go under, subside" (past tense sanc, past participle suncen), from Proto-Germanic *senkwan (cognates: Old Saxon sinkan, Old Norse sökkva, Middle Dutch sinken, Dutch zinken, Old High German sinkan, German sinken, Gothic sigqan), from PIE root *sengw- "to sink."

The transitive use (mid-13c.) supplanted Middle English sench (compare drink/drench) which died out 14c. Related: Sank; sunk; sinking. Sinking fund is from 1724. Adjective phrase sink or swim is from 1660s. To sink without a trace is World War I military jargon, translating German spurlos versenkt.
submerge (v.): c. 1600 (transitive), from French submerger (14c.) or directly from Latin submergere "to plunge under, sink, overwhelm," from sub "under" (see sub-) + mergere "to plunge, immerse" (see merge). Intransitive meaning "sink under water, sink out of sight" is from 1650s, made common 20c. in connection with submarines. Related: Submerged; submerging.
bombora: "A wave which forms over a submerged offshore reef or rock, sometimes breaking heavily and producing a dangerous stretch of broken water", 1930s: from an Aboriginal word, perhaps Dharuk bumbora.