Meaning

verb extend in one or more directions

verb become larger in size or volume or quantity

verb make bigger or wider in size, volume, or quantity

originRecorded in Middle English since 1422 (as expanden, expaunden), from Anglo-Norman espaundre, from Latin expandere (“to spread out”), itself from ex- (“out, outwards”) + pandō (“to spread”). Doublet of spawn.

Etymology from Wiktionary, CC BY-SA 3.0