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báculo m. (Noun) "staff"
16th cent. borrowing from Latin baculum 'id.' Of unknown origin. Borrowed from a non-Indo-European language with a root *bak(k)- "stick," "staff."
Indo-European
Romance
Portuguese báculo, Galician báculo, French bâcle, Italian bacolo
Celtic
Old Irish bacc "crooked staff," "hook" (< *bakko-), Old Welsh bach "hook," Old Breton bah 'id.,' Old Cornish bagh 'id.'
Germanic
Middle Dutch pegel "peg," Old English pægel "wine jug"
Balto-Slavic
Lithuanian bàkstelėti? "to thrust," Latvian bakstît? "to poke"
Hellenic
Ancient Greek βάκτρον (báktron) "stick" (< *bak-tro-), βακτηρία (baktería) "staff," "scepter" (< *bak-tér-)
Basque
Basque makila "walking stick," probably from Latin bacila "sticks," plural of baculum

"A more widely distributed (West Central) root for 'club' is *bak- (e.g. OIr bacc 'staff', Lat baculum 'staff', Grk báktron 'staff'; a Middle Dutch cognate pegge suplies NE peg); the initial b- has been explained either as the mark of a 'popular word' (i.e. one apparently used only in informal contexts and subject to the possibility of special phonological changes) or a loanword from some non-Indo-European language." ~ Mallory & Adams, The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World (2006)