The Spanish verb 'espantar' (to frighten) comes from the Latin word 'expaventare' meaning 'to frighten away.' This Latin word was formed by combining three elements: the prefix 'ex-' meaning 'outward,' the verb 'pavere' meaning 'to be frightened,' and the frequentative suffix '-tare' which indicated repeated action. Over time, 'expaventare' evolved into modern Spanish 'espantar,' where the 'x' sound simplified to 's' and the middle portion of the word contracted, a common pattern in the development from Latin to Spanish.

A related Spanish word is 'espanto' (fright, horror), which is the noun form derived from 'espantar.' You might also encounter 'espantoso' (frightful, horrible) and 'espantadizo' (easily frightened), which are all part of the same word family.

While English doesn't have any direct descendants from 'expaventare,' we do have some words that share the root 'pav-' from Latin 'pavere.' These include 'panic' and 'panic-stricken,' which come from the same Indo-European root that gave us Latin 'pavere.' Another related word is 'appall' (to horrify or dismay), which comes from Latin 'expallescere,' containing the same 'ex-' prefix and relating to becoming pale with fright.