busy (adj.)youdaoicibaDictYouDict
Old English bisig "careful, anxious," later "continually employed or occupied," cognate with Old Dutch bezich, Low German besig; no known connection with any other Germanic or Indo-European language. Still pronounced as in Middle English, but for some unclear reason the spelling shifted to -u- in 15c.

The notion of "anxiousness" has drained from the word since Middle English. Often in a bad sense in early Modern English, "prying, meddlesome" (preserved in busybody). The word was a euphemism for "sexually active" in 17c. Of telephone lines, 1893. Of display work, "excessively detailed, visually cluttered," 1903.
clutter (v.)youdaoicibaDictYouDict
1550s, "to collect in heaps," variant of clotern "to form clots, to heap on" (c. 1400); related to clot (n.). Sense of "to litter" is first recorded 1660s. Related: Cluttered; cluttering.