The Spanish verb 'expulsar' (to expel) comes from the Latin 'expulsare', which was a frequentative form of 'expellere' meaning 'to drive out'. The Latin 'expellere' itself was formed by combining two elements: the prefix 'ex-' meaning 'out' and the verb 'pellere' meaning 'to push or drive'. The frequentative form 'expulsare' indicated a repeated or intensive action of driving something out.

Some related Spanish words include 'pulsar' (to press or push), which comes from the same Latin root 'pellere'. Another related word is 'impulsar' (to drive forward or promote), which uses the prefix 'in-' (into) instead of 'ex-' (out) with the same base. These words share the core meaning of pushing or driving in different directions.

Several English words share this Latin ancestry, including 'expel', which comes directly from Latin 'expellere', and 'pulse', which relates to the pushing or beating motion from 'pellere'. The word 'compel' (to force or drive together) also comes from 'pellere' but with the prefix 'com-' (together). 'Repel' (to drive back) is another related word using the prefix 're-' (back). Understanding these connections can help remember that 'expulsar' involves the action of pushing or driving something out.