This is the 11059th most frequent Polish word.
frakach
"Frakach" is the locative plural form of "frak," meaning "tailcoats" in English.
Here, "frakach" is the locative case plural form of "frak", referring to formal attire called tailcoats.
W balowych frakach tańczyli całą noc.
They danced all night in ball tailcoats.
In this sentence, "fraki" is the nominative case plural form of "frak", referring to the same formal clothing in plural.
Uważaj na plamy, bo fraki są wypożyczone.
Be careful with stains, because the tailcoats are rented.
Here, "frakach" is again in the locative case plural form of "frak", paired with "sukniach wieczorowych" to describe the formal attire of attendees.