The only free and comprehensive online etymological dictionary of the Spanish language
peso (2) m. (Noun) "weight"
10th cent. From Latin pensum 'id.' See pensar.
Indo-European
Romance
Western Vuglar Latin Asturian pesu, Portuguese peso, Galician peso, Catalan pes, French pensum, Italian peso, Romanian păs, Sardinian pesu
picar (Verb) "to sting;" "to prick;" "to itch"
12th cent. From Vulgar Latin *piccare "to puncture," from Latin picus "woodpecker" (see pico (3)).
Indo-European
Romance
Asturian picar, Portuguese picar, Galician picar, Catalan picar
pico (1) m. (Noun) "peak," "point;" (slang) "penis"
11th cent. From pico (2), as a metaphor that a mountain peak resembles a bird's beak.
Indo-European
Romance
Asturian picu
pico (2) m. (Noun) "beak;" "mouth"
14th cent. From Latin beccus 'id.' The change from Latin b- to p- in Spanish was under influence from picar. Borrowed from a Celtic source (compare Gaulish beccus "beak"). From Proto-Celtic *bek(k)o- 'id.' Of unknown origin. Possibly borrowed from a substrate language or of imitative origin.
Indo-European
Romance
Asturian picu, Portuguese bico, Galician bico, Catalan bec, French bec, Italian becco
Basque
Gizpuzkoan moko "beak," "bill," Zuberoan mosko 'id.,' speculated by Mitxelena (1961) to be an expressive formation of beko "forehead;" possibly loanwords from the same Celtic source (see Trask 2008)
Picto (Adjective, Noun) "Pictish;" "Pict"
A scholarly term from Late Latin Picti "Picts," from Latin pictus "painted," the perfect passive participle of pingere "to paint" (see pintar). From Proto-Italic *pikto- 'id.' From Proto-Indo-European *piḱ-to- 'id.'
Indo-European
Celtic
Middle Welsh goruc "makes," Middle Cornish gruk "made"
Germanic
Gothic filu-faihs "many-colored," Old English fāh "colored" (Scots faw "variegated"), Old Saxon fēh "multicolored," Old High German fēh 'id.'
Balto-Slavic
Old Church Slavonic pьsati "to write," Russian pisátʹ 'id.,' Polish pisać 'id.' Old Prussian peisāi 'id.,' Lithuanian piẽšti "draws"
Hellenic
Mycenaean po-ki-ro-nu-ka "colored," Ancient Greek ποικίλος (poikílos) 'id.'
Indo-Iranian
Sanskrit piṣṭá- "adorned," Old Persian apinθa "to adorn"
pie m. (Noun) "foot"
12th cent. From Latin pedem, accusative of pes 'id.' From a pre-form *peds 'id.,' taken from the oblique stem *ped- "foot" in Proto-Italic. Replaced the earlier Proto-Italic stem *pōd-. From Proto-Indo-European *pōd- 'id.'
In the plural we find piedes until the 15th cent.
Indo-European
Romance
Asturian pie, Portuguese , Galician , Catalan peu, French pied, Italian piede, Aromanian pezã, Romanian piez, Sardinian pee
Italic
Oscan pedú "foot," Umbrian peři "by the foot"
Germanic
Gothic fotus "foot," Old Norse fótr 'id.,' Old High German fuoz 'id.,' Old Saxon fōt 'id.,' English foot
Hellenic
Ancient Greek πώς (pós) "foot," Mycenaean po-de 'id.'
Armenian
Armenian otn "foot"
Indo-Iranian
Sanskrit pā́t "foot," Young Avestan pad- 'id.'
piedra f. (Noun) "rock"
11th cent. From Latin petra 'id.' Borrowed from Ancient Greek πέτρα ‎(pétra) 'id.' Of unknown origin. Presumably borrowed from another language.
Indo-European
Romance
Asturian piedra, Portuguese pedra, Galician pedra, Catalan pedra, French pierre, Italian pietra, Aromanian cheatrã, Romanian piatră, Sardinian pedra
piel f. (Noun) "skin"
10th cent. Old Spanish pielle; after 12th cent., piel. From Latin pellis 'id.' From Proto-Italic *pelni- 'id.' From Proto-Indo-European *pel-ni̯- 'id.' From a root *pel- of unknown meaning.
Indo-European
Romance
Asturian piel, Portuguese pele, Catalan pell, French peau, Italian pelle, Aromanian cheali, Romanian piele, Sardinian pedhe
Germanic
Gothic þruts-fill "leprosy," Old Norse fjall "skin," Old High German fel 'id.,' Old English fell 'id.'
Balto-Slavic
Old Church Slavonic pelena "swathing band," Russian pelená "shroud," Czech plena "headscarf," Slovene plẹ́na "bandage," Lithuanian plėnė̃ "membrane"
Hellenic
Ancient Greek πελλοράφος (pelloráphos) "sewing hides together"
piélago m. (Noun) "high sea"
13th cent. From Latin pelagus "sea." Borrowed from Ancient Greek πέλαγος ‎(pélagos) 'id.' Of Pre-Greek origin.
Indo-European
Romance
Asturian piélagu, (many non-standard dialects) pielgu, Portuguese pego, pélago, Italian pelago
pielga f. (Noun) (Salamanca) "wooden cattle hitch measuring 30 cm"
From a pre-form *pelga, from Latin pedica "fetters," "snare." The d developed into -l- due to palatization and syncopation in Vulgar Latin. Latin pedica is from a surviving weak stem ped- "foot" in Latin, from Proto-Italic *ped- 'id.' For a continued etymology, see pie.
Regarding the Latin stem ped- and the nominative singular pes "foot:" the stem is from the Proto-Italic genitive *ped-s via Lachmann's Law, where *-d was lost while *-e- underwent compensatory lengthening, and replaced the Proto-Italic nominative singular *pōd-.