"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.
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.).
late 14c., "that can be felt, perceptible by the touch," from Late Latin palpabilis "that may be touched or felt," from Latin palpare "touch gently, stroke," a word de Vaan finds to be of no known etymology (rejecting the connection in Watkins, etc., to a reduplication of the PIE root *pal-, as in feel (v.), on phonetic grounds). Some sources suggest it is onomatopoeic. The figurative sense of "easily perceived, evident, clear, obvious" also is from late 14c., on the notion of "seeming as if it might be touched." Related: Palpably; palpability.
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).
early 13c. (c. 1200 in Anglo-Latin), "stake, pole, stake for vines," from Old French pal and directly from Latin palus "stake, prop, wooden post" (source also of Spanish and Italian palo), which is from PIE *pakslo-, suffixed form of root *pag- "to fasten." A doublet of pole (n.1).
From late 14c. as "fence of pointed stakes." Paler as a surname meaning "fence-builder" is recorded from late 12c. Another Middle English form of the word in the "fence, paling, wall of an enclosure" sense, based on the plural, was pales, palis (late 14c.), and the surname Paliser is attested from early 14c.
The figurative sense of "limit, boundary, restriction" is from c. 1400, and survives (barely) in beyond the pale and similar phrases. Meaning "the part of Ireland under English rule" is by 1540s (the thing itself dates to the conquests of Henry II), via the notion of "enclosed space," hence "district or region within determined bounds," hence "territory held by power of a nation or people" (mid-15c.).
"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.