suddenly; abruptly; unexpectedly
Rare literary adverb; modern Japanese normally uses 突然, 急に, or いきなり instead.
In old novels, 忽地 is sometimes read as こっち and indicates a sudden event.
こちら is the polite, formal way to say 'this way/here/this one/I', while こっち is the casual everyday equivalent used with friends and family.
The derivation is uncertain; the kanji 忽地 are used as ateji for the reading こっち, likely representing an older adverbial form.