The Spanish verb 'influir' (meaning 'to influence') comes from the Latin verb 'influere', which literally meant 'to flow into'. This Latin word was formed by combining two elements: the prefix 'in-' meaning 'into, within' and the verb 'fluere' meaning 'to flow'. The metaphorical sense of influence as something that 'flows into' and affects something else developed from this literal meaning of liquid flowing into a container or space.

Several common Spanish words share this Latin root 'fluere' (to flow). For example: 'fluir' (to flow), 'fluido' (fluid), and 'afluente' (tributary, literally 'flowing toward'). The connection between these words and 'influir' is clear when you think about influence as a kind of flowing or movement of ideas or power from one person or thing to another.

Many English words are related to 'influir' through the same Latin root. The most obvious is 'influence' itself, but also 'fluid', 'fluent', 'affluent' (originally meaning 'flowing toward', now meaning 'wealthy'), and 'influx' (a flowing in). All these words maintain some connection to the original concept of 'flowing' - whether literally about liquids or metaphorically about the flow of ideas, power, or wealth.