scuba

Scuba began as SCUBA, an acronym for 'self-contained underwater breathing apparatus.' Each piece traces back through English: 'self-contained' from Old English self and Latin continēre (to hold together), 'underwater' from Old English under- and wæter, 'breathing' from Middle English brethen plus the -ing suffix, and 'apparatus' from Latin apparātus, itself from ad- and parō (to prepare).

What started as a technical label for the equipment's design — that it carried its own air supply — was compressed into a single pronounceable word, SCUBA, which lowercased into scuba as everyday speech took over.

It shares roots with 'contain,' since 'self-contained' descends from Latin continēre through Old French contenir and Middle English conteinen.