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dual [dual 词源字典]: dual: [17] Dual was borrowed from Latin duālis, a derivative of duo ‘two’ (which is a distant relative of English two). In Latin it was used particularly by grammarians, to denote the category ‘two people or things’ (as opposed to the plural, referring to three or more), and this was the earliest sense of the word adopted by English. (Incidentally, despite its formal similarity, and a common meaning element – two people participate – duel [15] is not etymologically related to dual; it comes from medieval Latin duellum, which was originally an archaic form of Latin bellum ‘war’.
=> two[dual etymology, dual origin, 英语词源]
bellicose (adj.): early 15c., "warlike," from Latin bellicosus "warlike, valorous, given to fighting," from bellicus "of war," from bellum "war," Old Latin duellum, dvellum, which is of uncertain origin.
Bellona: Roman goddess of war, from Latin bellum "war," Old Latin duellum, dvellum, which is of uncertain origin.
duel (n.): 1590s (from late 13c. in Latin form), from Medieval Latin duellum "combat between two persons," by association with Latin duo "two," but originally from Latin duellum "war," an Old Latin form of bellum (see bellicose). Retained in poetic and archaic language and apparently given a special meaning in Medieval or Late Latin of "one-on-one combat" on fancied connection with duo "two."
duel (v.): 1640s, see duel (n.). Related: Dueled; dueling; duelling.