One who floats or something that floats; an archaic spelling of 'floater'.
From 'flote' (archaic form of float) plus the agent suffix '-er' (meaning 'one who does'). This older form survives in historical documents and some technical contexts.
The '-er' suffix is one of English's oldest word-making tools—it goes back to Old English and lets us turn almost any verb into a person or thing that does that action (runner, teacher, swimmer)!
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