The Spanish verb 'peligrar' (meaning 'to be in danger') comes from the Spanish noun 'peligro' ('danger') combined with the verbal suffix '-ar'. The noun 'peligro' evolved from Old Spanish 'periglo', which in turn came from Latin 'periculum' meaning 'danger, risk, trial'. The development from Latin to modern Spanish shows a typical pattern where the medial '-cu-' sound shifted to '-g-', and the final syllable was simplified.

The most obvious related Spanish word is the noun 'peligro' (danger), which is actually the base word from which 'peligrar' was formed. Spanish speakers also use the adjective 'peligroso' (dangerous), which is derived from the same root. These words form a family of related terms all conveying the concept of danger or risk.

English speakers might recognize the connection to words like 'peril' and 'perilous', which come from the same Latin root 'periculum'. The English words maintained a spelling and pronunciation closer to the original Latin, while the Spanish terms underwent more sound changes over time. When you see 'peligrar', you can think of something being 'in peril' to help remember its meaning.