'raring' originates from English, arising in dialectal and colloquial use as an intensive/adjectival form (early 19th century) of an older adjective meaning 'fierce/violent' or 'exceptional', formed with the -ing suffix to express a strong state.

'raring' was used regionally in earlier English with senses of 'violent, fierce, or tumultuous' and later developed a figurative sense of high readiness or eagerness; by the 19th century the idiomatic phrase 'raring to go' had emerged to mean 'very eager to begin'.

Initially it carried senses close to 'violent' or 'boisterous', but over time it shifted toward the present sense of 'very eager' (often positively connoted).