flus·ter (flŭs'tər) tr. & intr.v.
flus·tered, flus·ter·ing, flus·ters To make or become nervous or upset. n. A state of agitation, confusion, or excitement.
[From Middle English flostring, agitation, probably of Scandinavian origin; see pleu- in Indo-European roots.]
1422 (implied in flostyrynge), from a Scand. source (cf. Icel. flaustr "bustle," flaustra "to bustle"). Originally "to excite," especially with drink; sense of "to flurry, confuse" is from 1724.