The Spanish verb 'peinar' (to comb) comes from the Latin verb 'pectinare', which also meant 'to comb'. The Latin 'pectinare' itself was derived from the Latin noun 'pecten', meaning 'comb'. During the evolution from Latin to Spanish, the consonant cluster 'ct' simplified to 'i', a common sound change in Spanish, giving us the modern form 'peinar'.

A related Spanish word is 'peine' (comb), which is also derived from the Latin 'pecten'. This noun-verb pair ('peine'/'peinar') maintains the close semantic relationship of the original Latin words.

The English word 'pectinate', meaning 'having branches or parts arranged like the teeth of a comb', comes from the same Latin root 'pecten'. This technical term is mostly used in scientific contexts, such as biology and anatomy. Another related English word is 'pectoral', as in 'pectoral muscles', which originally referred to the comb-like arrangement of the chest muscles.