ebullient \ih-BUL-yuhnt\ (adjective) - 1 : Overflowing with enthusiasm or excitement; high-spirited. 2 : Boiling up or over.
"He was extremely nervous and extremely jealous of other tenors and he covered his nervous jealousy with an ebullient friendliness." -- James Joyce, 'Dubliners'
Ebullient comes from Latin ebullire, "to bubble up," from e-, "out of, from" + bullire, "to bubble, to boil."