"partner, mate, chum," slang, 1680s, said to be from Romany (English Gypsy) pal "brother, comrade," a variant of continental Romany pral, plal, phral, which are probably from Sanskrit bhrata "brother" (from PIE root *bhrater- "brother"). Colloquial extended form palsy-walsy is attested from 1930. Pally (adj.) is attested by 1895.
"behave as pals; spend time or pursue activities together," 1879, from pal (n.). Originally with in; by 1889 with up; 1915 with round or around. Related: Palled; palling.
bhrāter-, Proto-Indo-European root meaning "brother."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhrátár-, Old Persian brata, Greek phratér, Latin frater, Old Irish brathir, Welsh brawd, Lithuanian broterėlis, Old Prussian brati, Old Church Slavonic bratru, Czech bratr, Polish brat, Russian bratŭ, Kurdish bera; Old English broþor, Old Norse broðir, German Bruder, Gothic bróþar.
also side-kick, "companion or close associate," 1901, also side-kicker (1903, "O. Henry"), American English, of uncertain signification. Earlier terms were side-pal (1886), side-partner (1886).
"short iron bar acting as a catch or brake preventing a capstan from recoiling" (nautical) 1620s, of unknown origin; perhaps from French pal "stake" [OED] or épaule "shoulder" [Klein]. Extended to similar devices in other machinery.
1650s, "nourishment," also "allowance to a wife from a husband's estate, or in certain cases of separation," from Latin alimonia "food, support, nourishment, sustenance," from alere "to nourish, rear, support, maintain" (from PIE root *al- (2) "to grow, nourish") + -monia suffix signifying action, state, condition (cognate with Greek -men). Derived form palimony was coined 1979, from pal (n.). Related: Alimonious.
"one who avoids company," 1946; see lone. Apparently first in U.S. baseball slang:
Ted [Williams] is likable enough in spite of his obsession with his specialty. He is something of a "loner," and he refuses to pal around with his teammates in off hours, but in the clubhouse he does his share of the talking. [Life magazine, Sept. 23, 1946]
Middle English pal, from Old English pæll "rich cloth or cloak, purple robe, altar cloth," from Latin pallium "cloak, coverlet, covering," in Tertullian, the garment worn by Christians instead of the Roman toga; related to pallo "robe, cloak," palla "long upper garment of Roman women," perhaps from the root of pellis "skin." The notion of "cloth spread over a coffin" (mid-15c.) led to figurative sense of "dark, gloomy mood" (1742). The earlier figurative sense is "something that covers or conceals" (mid-15c.).