The only free and comprehensive online etymological dictionary of the Spanish language
consigo (Adverb) "with him, her, it"
Prefix con- "with" added to Old Spanish sigo "with him, her, it," from Latin secum 'id.,' a compound of se, third-person pronoun, and cum "with."
Indo-European
Romance
Portuguese cônsul, French consul, Italian console
Celtic
Old Irish selb "possession," Welsh helw 'id.'
Germanic
Gothic saljan "to sacrifice," Old Norse selja 'id.,' Old High German sellan "to sell," Old Saxon gi-sellian 'id.,' Old English sellan 'id.' (English to sell)
Hellenic
Ancient Greek ἑλεῖν (eleîn) "to take"

The word secum in Latin became *sego/*sigo in Vulgar Latin. The phonological change from -cum to -go led to confusion of its meaning, as it was no longer identifiable as the word cum "with." By the time of Old Spanish, the word (now evolved into sigo) was unclear and con- was added to reinforce its meaning. The same process happened in conmigo, contigo.

Final updates in preparation for a particularly large data update coming at the end of the month.
The Online Etymological Dictionary of Spanish is a free etymological dictionary of the Spanish language launched on August 6, 2016. An etymology is not a definition but a history of a word over time. This site provides an account of the development of the Spanish language as best as historical linguists are able to ascertain in a way that is accessible both by laymen and academics. If you enjoy using this dictionary, please consider donating to help keep this site alive.