Despite an extensive search, the meaning of the word "Jirjis" (جِرْجِیْس) could not be found in reliable sources. However, some books mention that "Jirjis" was the name of a righteous man from the Bani Israel. Based on this connection, it would be acceptable to use "Jirjis" as a name.
Allah the Almighty knows best.
Darul Ifta Al-Ikhlas, Karachi.
سنن ابی داؤد: (رقم الحدیث: 4955، ط: دار ابن حزم)
عن أبي الدرداء قال: قال: رسول الله صلی اللہ علیه وسلم: تُدعون یوم القیامة بأسمائکم وأسماء آبائکم فأحسنوا أسمائکم․