Seomra is a masculine noun that means room.
Folctha is the past participle of the verb folc, meaning wash, bathe.
Thus, seomra folctha: bathroom.
The euphemistic use of 'the bathroom', common in some dialects of English, is not found in Irish. Use (an) leithreas or, more colloquially, (an) tigín to refer to (the) toilet. Other common colloquial forms include: