1787, from alarming, present-participle adjective from alarm (v.), + -ly (2).
It grew alarmingly fast
Alan
alar
Alaric
alarm
alarmed
alarmingly
alarmist
alarum
alas
Alaska
alastor
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}