Webster's 1828 Dictionary
TWITTERING
ppr. Uttering a succession of small interrupted sounds, as in a half suppressed laugh, or as a swallow.
Webster's 1913 Dictionary
TWITTERING
TWITTERING Twit "ter *ing, n.
1. The act of one who, or that which, twitters.
2. A slight nervous excitement or agitation, such as is caused by desire, expectation, or suspense. A widow, who had a twittering towards a second husband, took a gossiping companion to manage the job. L'Estrange.
The Wordsmith Dictionary