Spat

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early 19th century: abbreviation of spatterdash.

wiktionary

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Old English spittan, spætan.

Of uncertain origin; perhaps related to spit.

Shortening of spatterdash, from spatter + dash. 1779.

1804. American English, probably imitative.

Attested from 1823.

Latin spatium(“space”)

etymonline

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spat (n.1)

"petty quarrel," 1804, American English, of unknown origin; perhaps somehow imitative (compare spat "smack, slap," attested from 1823).

spat (n.2)

"short gaiter covering the ankle" (usually only in plural, spats), 1779, shortening of spatterdash "long gaiter to keep trousers or stockings from being spattered with mud" (1680s), from spatter and dash (v.).

spat (n.3)

"spawn of a shellfish," especially "spawn of an oyster," also "a young oyster," 1660s, of unknown origin, perhaps from the past tense of spit (v.1).