armada

Borrowed from Spanish armada, meaning "fleet, navy," which comes from Medieval Latin armāta, itself the feminine past participle of Latin armō, "to arm," rooted in arma, "weapons."

The word simply passed from Spanish into English carrying its meaning of a fleet or navy intact, with no major shift recorded.

It's a doublet of army — both words trace back to the same Latin root armō, meaning "to arm," just filtered through different paths into English.