The Spanish verb 'mostrar' (to show) comes from the Latin verb 'monstrare' meaning 'to show or point out.' Going further back, 'monstrare' developed from the Latin noun 'monstrum' meaning 'omen or supernatural occurrence.' 'Monstrum' itself was formed by combining the Latin verb 'monere' (to warn or advise) with the instrumental suffix '-trum'. This etymology reveals how the concept of showing or demonstrating something evolved from earlier meanings related to warnings and supernatural signs.

A related Spanish word is 'demostrar' (to demonstrate or prove), which shares the same Latin root. The word 'muestra' (sample or display) is also derived from 'mostrar'. These words maintain the core meaning of showing or displaying something.

Several English words share this Latin ancestry, including 'monster' and 'demonstrate'. 'Monster' comes directly from Latin 'monstrum' and originally meant an omen or divine portent before evolving to mean a frightening creature. 'Demonstrate' comes from 'monstrare' with the prefix 'de-', maintaining the meaning of showing or proving something. The word 'monitor' is also related, coming from Latin 'monere', and keeps the sense of watching or warning.