Continuing the discussion of "click" and similar words in German, French and Spanish, here’s an interesting comment from the Oxford English Dictionary: “In English and Germanic generally, [click] appears to stand in ablaut relation to clack, as expressing a thinner and lighter sound; compare chip, chap, clip, clap, clink, clank.”
“Ablaut” means a change of vowel in related words or forms, such as in irregular verbs like sing, sang, sung. But those are different forms of a verb and we’re talking about onomatopoetic or echoic words: ones that imitate a sound. Changing from a “short i” in click, chip, clip or clink to “short a” as in clack, chap, clap or clank does seem to indicate the same kind of sound but lower pitched and heavier. Clunk is even heavier.
Linguists call the “short i” in click a “high vowel,” meaning the tongue is near the roof of the mouth. The “short a” in clack is relatively low; the mouth is more open. Strangely, however, the higher the tongue, the lower the pitch or frequency of the vowel. Nevertheless, we associate the “short i” sound as in click, tinkle, titter, pin with thin, tinny light things and the “short a” in clank, jangle, laugh and tack with heavier, more substantial things.
The “uh” sound in clunk is in the middle of the vowel range, but words like clunk, thump, jump, bump, dump, rump and plunk sound heaviest of all—lumbering, cumbersome and klutzy.