Sam

wiktionary

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Acronym

From Middle English sammen, samnen, from Old English samnian, ġesamnian(“to collect, assemble, bring together, gather, join, unite, compose, meet, glean”), from Proto-Germanic *samnōną(“to gather”), from Proto-Indo-European *sem-(“one”). Cognate with Dutch zamelen(“to collect”), German sammeln(“to collect, gather”), Swedish samla(“to gather, collect”), Icelandic samna(“to gather, collect”). More at same.

From Middle English sām(“together”), from Old English samen(“together”), from Proto-Germanic *samanai(“together”), from Proto-Indo-European *sem-(“together, one”).

From Middle English sam-(prefix), from Old English sām-(“half-; partly; incompletely”), from Proto-Germanic *sēmi-(“half”), from Proto-Indo-European *sēmi-(“half”). Related to semi- (via Latin).

Possibly from Uncle Sam.

etymonline

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SAM

1958, acronym for surface to air missile.