Romanes eunt domus
Romanes is not a word. The ending looks like that of a 3rd declension ending, but Romanus is the nominative and Romani (2nd declension) is the plural form of this adjective being used as a noun.
Eunt is from the verb “to go” ire or eo “I go.”
Present Indicative
Singular 1 eo
2 is
3 it
Plural 1 imus
2 itis
3 eunt