In English, German, and Dutch, the primary sense has become "to salute," but the word once had much broader meaning. Perhaps originally "to resound" (via notion of "cause to speak"), causative of Proto-Germanic *grætanan, root of Old English grætan (Anglian gretan) "weep, bewail," from PIE *gher- (2) "to call out." Greet still can mean "cry, weep" in Scottish & northern England dialect, though this might be from a different root. Grætan probably also is the source of the second element in regret. Related: Greeted; greeting.
Old English felan "to touch or have a sensory experience of; perceive, sense (something)," in late Old English "have a mental perception," from Proto-Germanic *foljanan (source also of Old Saxon gifolian, Old Frisian fela, Dutch voelen, Old High German vuolen, German fühlen "to feel," Old Norse falma "to grope"), which is of uncertain origin, possibly from a PIE *pal- "to touch, feel, shake, strike softly" (source also of Greek psallein "to pluck" the harp), or from PIE root *pel- (5) "to thrust, strike, drive."
In Germanic languages, the specific word for "perceive by sense of touch" has tended to evolve to apply to the emotions. The connecting notion might be "perceive through senses which are not referred to any special organ." Sense of "be conscious of a tactile sensation, sense pain, pleasure, illness, etc.; have an emotional experience or reaction," developed by c. 1200, also "have an opinion or conviction;" that of "to react with sympathy or compassion" is from mid-14c. Meaning "to try by touch" is from early 14c. From late 14c. as "know (something) beforehand, to have foreknowledge of." To feel like "want to" attested from 1829.
Middle English plukken, "pull (something) off or out from a surface" (especially hair or feathers, but also teeth), from late Old English ploccian, pluccian "pull off, cull," from West Germanic *plokken (source also of Middle Low German plucken, Middle Dutch plocken, Dutch plukken, Flemish plokken, German pflücken). This is perhaps from an unrecorded Gallo-Roman or Vulgar Latin *piluccare (source of Old French peluchier, late 12c.; Italian piluccare), a frequentative, ultimately from Latin pilare "pull out hair," from pilus "hair" (see pile (n.3)). But despite the similarities, OED finds difficulties with this and cites gaps in historical evidence. From late 14c. as "to pull sharply with a sudden jerk or force (of the strings of a bow, harp, etc.). Related: Plucked; plucking.
To pluck a rose, an expression said to be used by women for going to the necessary house, which in the country usually stands in the garden. [F. Grose, "Classical Dictionary of the Vulgar Tongue," 1785]
This euphemistic use is attested from 1610s. To pluck up "summon up" (courage, heart, etc.) is from c. 1300.
Middle English slēn, from Old English slean "to smite, strike, beat," also "to kill with a weapon, slaughter" (class VI strong verb; past tense sloh, slog, past participle slagen), from Proto-Germanic *slahanan "to hit" (source also of Old Norse and Old Frisian sla, Danish slaa, Middle Dutch slaen, Dutch slaan, Old High German slahan, German schlagen, Gothic slahan "to strike"). The Germanic words are said to be from PIE root *slak- "to strike" (source also of Middle Irish past participle slactha "struck," slacc "sword"), but, given certain phonetic difficulties and that the only cognates are Celtic, Boutkan says the evidences "point to a North European substratum word."
The verb slēn displays many nondialectal stem variants because of phonological changes and analogical influences both within its own paradigm and from other strong verbs. [Middle English Compendium]
Modern German cognate schlagen maintains the original sense of "to strike." Meaning "overwhelm with delight" (mid-14c.) preserves one of the wide range of meanings the word once had, including, in Old English, "stamp (coins); forge (weapons); throw, cast; pitch (a tent), to sting (of a snake); to dash, rush, come quickly; play (the harp); gain by conquest."
Old English meaning "ligaments, tendons" is preserved in hamstring (n.), heart-strings. Meaning "limitations, stipulations" (1888) is American English, probably from the common April Fool's joke of leaving a purse that appears to be full of money on the sidewalk, then tugging it away with an attached string when someone stoops to pick it up.
To pull strings "control the course of affairs" (1860) is from the notion of puppet theater. First string, second string, etc. in athletics (1863) is from archers' custom of carrying spare bowstrings in the event that one breaks. Strings "stringed instruments" is attested from mid-14c. String bean is from 1759; string bikini is from 1974.