From harvest + -man. (sense 2): There are various hypotheses and folk etymologies for why the arachnids are called harvestmen, but the most likely explanation is the shape of their legs, which resemble sickles or scythes. More information The association with harvesting or haymaking is found across Europe; compare words for “harvest spider” in other languages: Dutch hooiwagen (literally “hay-cart”), Welsh medelwr (literally “reaper, harvester”), Irish Pilib an fhómhair (literally “Philip of the harvest”), Danish mejer (literally “mower, reaper”), French faucheur (literally “scyther”), Spanish segador (literally “reaper, harvester, mower”) and agostero (literally “August-er”), Czech sekáč (literally “reaper, mower; warrior”), Polish kosarz (literally “reaper, mower, haymaker”), Russian сенокосец (senokosec, literally “little haymaker”) and косиножка (kosinožka, literally “little scythe-leg”), Ukrainian косарик (kosaryk, literally “mower”), Hungarian kaszáspók (literally “scyther-spider”), Serbo-Croatian pauk kosac (literally “reaper spider”), and even modern Hebrew קוצר (kotsér, originally “shortener”, literally “reaper, harvester”). Further compare German Schneider (literally “cutter; tailor”), Swiss Zimmermann (literally “carpenter”) and Welsh teiliwr (literally “tailor”). (Can this⁽⁺⁾ etymology be sourced? )

carter • daddy longlegs • harvest spider • grandfather-graybeard • harry-longlegs • shepherd spider • daddy longleg