The Spanish verb 'pecar' (to sin) comes directly from the Latin verb 'peccare', which meant 'to sin' or 'to make a mistake'. The word maintained its meaning as it evolved from Latin to Spanish, with the main changes being phonological - the double 'cc' was simplified to a single 'c', and the Latin infinitive ending '-are' became the Spanish infinitive ending '-ar'.

Some common Spanish words related to 'pecar' include 'pecado' (sin), 'pecador' (sinner), and 'pecaminoso' (sinful). These words are all derived from the same Latin root and form a family of words related to the concept of sin and wrongdoing.

While English doesn't have any direct cognates of 'pecar', we do have some words borrowed from the same Latin root, such as 'peccadillo' (a small sin or minor fault) and 'impeccable' (without sin or fault, perfect). The word 'impeccable' combines the Latin 'in-' (meaning 'not') with 'peccare', literally meaning 'not able to sin' or 'without fault'.