Alexander

wiktionary

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Unknown. Apparently from either the given name or the surname Alexander, but the connection is unclear. Attested since the early 20th century.

etymonline

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Alexander

masc. proper name, from Latin, from Greek Alexandros "defending men," from alexein "to ward off, keep off, turn (something) away, defend, protect" + anēr (genitive andros) "man" (from PIE root *ner- (2) "man"). The first element perhaps is related to Greek alke "protection, help, strength, power, courage," alkimos "strong;" and cognate with Sanskrit raksati "protects," Old English ealgian "to defend."

As a kind of cocktail recipe featuring crème de cacao and cream, Alexander is attested from 1913; the reason for the name is unclear.