Frank Schellhardt, head of the zoo's great apes enclosure "Pongoland", told DPA news agency "we gave him the African name Yengo, it means 'strong.'"
Yengo was born in December and now weighs about three kilograms.
Although mother ape Kibara gave birth to Yengo two-and-a-half months ago, keepers were unable to be sure of his sex until now, because gorillas keep their young so close in the first few weeks.
"At this age, the child is always held very tightly to the mother. She usually carries them, only rarely putting them down and even then only for a short time," Schellhardt said.
When Kibara needed a break, the baby's grandmother Viringika would immediately take over looking after him, making it difficult for keepers to examine Yengo and find out the sex.