'arroyuelo' originates from Spanish, specifically the word 'arroyo' plus the diminutive suffix '-uelo' (from Latin diminutive suffixes such as '-ulus'), where 'arroyo' ultimately comes from Latin 'rīvus' meaning 'stream' or 'brook'.

'rīvus' (Latin) developed into Romance forms and Old Spanish (e.g. early forms like 'arroio'/'arroyo'), and the modern Spanish diminutive formation produced 'arroyuelo'.

Initially it referred to a 'stream' in the sense of Latin 'rīvus'; over time in Spanish the base 'arroyo' came to mean 'stream' or 'brook', and 'arroyuelo' emerged as the diminutive meaning 'small stream' or 'little brook'—its meaning has remained close to the original sense.