1570s, “a deviation in argument,” also “a military sally,” from Latin excursionem (nominative excursio) “a running forth, sally, excursion, expedition,” figuratively “an outset, opening,” noun of action from past-participle stem of excurrere “run out, run forth, hasten forward; project, extend,” from ex “out” (see ex-) + currere “to run” (from PIE root *kers- “to run”). Sense of “journey” recorded in English by 1660s.
In symbiont, we do not only host events in house, we also regularly go out, into the “field”. Be it swamps, libraries, canals, urban deserts – the public space is the biggest non white cube we can think of.