In a 1992 developer interview, it was revealed that Cú Chulainn's name and design were inspired by Cú Chulainn from Yousei-ou manga series.

The attached image shows Shin Megami Tensei’s Cú Chulainn design (left) and its inspiration, the Cú Chulainn character from the Ryoki Yamagishi manga Yousei-ou (right).
Contributed by ProtoSnake
Attachment
Attachment