Origins
The English word 'entertain' entered the language in the late fifteenth century, borrowed from Old French 'entretenir,' a compound of 'entre-' (among, between, from Latin 'inter') and 'tenir' (to hold, from Latin 'tenere'). The literal meaning is 'to hold among' — to keep something or someone held within a social or mental space.
The word's semantic development in English is a study in how a single metaphor can branch into seemingly unrelated meanings that all remain connected at the root.
The earliest English sense of 'entertain' was 'to maintain' or 'to keep in a certain condition' — close to the Old French meaning. One could 'entertain' a fortification (maintain it), 'entertain' an army (keep it provisioned), or 'entertain' a friendship (keep it alive). This sense is now obsolete in everyday usage but survives in the phrase 'to entertain a notion' or 'to entertain an idea,' which means to hold a thought in mind, to maintain it among one's considerations.
Development
The hospitality sense — to receive and host guests — emerged by the early sixteenth century. To entertain guests was to hold them among your household, to receive them into your domestic space and provide for their comfort and pleasure. This sense connects directly to the etymological meaning: the host holds the guest among (inter) the resources and society of the household.
From hosting guests, the word naturally extended to the specific acts of amusement and enjoyment that a host might provide. If entertaining guests meant hosting them, then entertainment was whatever kept them engaged and pleased — music, stories, games, feasting. By the late sixteenth century, 'entertainment' had become an independent concept, no longer tied to specific acts of hospitality but referring to any form of amusement or diversion.
The modern entertainment industry — film, television, music, gaming, streaming — uses the word in this fully abstracted sense. An 'entertainer' is someone whose profession is providing amusement, whether as an actor, musician, comedian, or performer of any kind. The 'entertainment industry' is one of the largest sectors of the global economy, and its name traces back to the simple metaphor of a medieval host holding guests among pleasant things.
Latin Roots
The intellectual sense — 'to entertain an idea' — is actually the oldest surviving branch of the word's meaning in English. When one entertains a hypothesis, a proposal, or a possibility, one is doing exactly what the Latin etymology describes: holding it among (inter) one's thoughts, giving it temporary residence in the mind, neither accepting nor rejecting it but keeping it present for examination. This is the most etymologically faithful sense of the word, yet it is often perceived as a secondary or metaphorical extension of the 'amusement' meaning.
French 'entretenir' retained a broader semantic range than its English descendant. In modern French, 'entretenir' primarily means 'to maintain' or 'to keep up' (entretenir une maison, to maintain a house; entretenir des relations, to maintain relations), and 'un entretien' is a conversation or an interview — an exchange held between (entre) people. The French word preserved the 'maintain' and 'converse' senses that English largely dropped.
Within the '-tain' family, 'entertain' is the most semantically adventurous member. Where 'contain' holds together, 'detain' holds back, 'retain' holds onto, 'maintain' holds up, 'sustain' holds from below, 'obtain' reaches toward, and 'abstain' holds away, 'entertain' holds among — keeping someone or something engaged within a social or cognitive space. The prefix 'inter-' (among) gives it a uniquely social character: entertaining is fundamentally about the interaction between a host and guests, between a mind and its ideas, between a performer and an audience.
Legacy
The transition of 'entertain' from a general-purpose word meaning 'to maintain' to a specialized word meaning 'to amuse' reflects a broader cultural shift. As European societies became more affluent and leisured, the specific act of providing amusement became economically and culturally important enough to claim a dedicated word. That the English language repurposed a word meaning 'to hold among' for this purpose says something about how entertainment was understood: as the art of holding people's attention, keeping them engaged within a shared experience of pleasure.