Etymology
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bunker (n.)
1758, originally Scottish, "seat, bench," a word of uncertain origin, possibly a variant of banker "bench" (1670s; see bank (n.2)); or possibly from a Scandinavian source (compare Old Swedish bunke "boards used to protect the cargo of a ship"). Meaning "receptacle for coal aboard a ship" is from 1839. Of sand-holes on golf courses, by 1824, from the extended sense "earthen seat" (1805). The meaning "dug-out fortification" probably is from World War I.
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bunk (n.1)
1758, "sleeping-berth in a vessel," later in a railroad car, etc., probably a shortened form of bunker (n.) in its sense of "seat." Bunk-bed (n.) attested by 1869.
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sand-trap (n.)

1838, in hydraulics, "device for filtering impurities from water," from sand (n.) + trap (n.). As "golf bunker," by 1906.

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