sondar

to sound (to probe the depth of water with a weighted rope or similar); to catheterize

Borrowed from French sonder, from Old French sonder, from sonde (“sounding line”), extracted from Old English sundline (“sounding line”), from sund (“water, sea, swimming, sound (channel)”) from Proto-Germanic *sundą (“swimming; sound”), cognate with English swim. An alternative theory derives it from a hypothetical Vulgar Latin *subundāre, from Latin sub- + undō (“to surge, to swell”), from unda (“wave”).