Where does “pillbug” come from?

pillbug (English) comes from English Pill, from Welsh pil, from English Peel, from Old French piller, from Latin piliō, from Latin pilō, from Latin pila, from Latin pīlus — to grind, to crush.

Ancestry of “pillbug”, step by step

pillbug traces back through two separate lines of ancestry.

via English Pill

StepLanguageWordMeaning
1EnglishPillOS grid ref ST5275
2Welshpilpeel, rind
3EnglishPeelA placename
4Old FrenchpillerAlternative form of pillier; pillage; plunder
5Latinpiliō
6Latinpilōto put forth hairs, grow hairy
7Latinpilamortar; pillar; pier
8Latinpīlusa hair
9Latinpīluma pounder, pestle
10Proto-Italicpistlom
11Proto-Indo-Europeanpis-tlo-
12Proto-Indo-Europeanpeys-to grind, to crush

via English Bug

StepLanguageWordMeaning
1EnglishBugA Volkswagen Beetle car; A Bugatti car
2Englishbuggebeetle
3Middle Englishbuggebogy, hobgoblin, bugbear; scarecrow
4Proto-Germanicbugja-swollen up, thick
5Proto-Indo-Europeanbʰew-to grow, swell; to swell, wax, grow; to blow; to...
Every word from Proto-Indo-European peys-