Search gender: all male female Gennai Boy Name Meaning, Kanji Variations. 1 names found. gender: all male female Name: gennai Katakana: ゲンナイ 0 Kanji: 源内 Meaning: 源Source. The source from which the water of a river flows. The beginning of something happening. 内Inside. You can save your favorite names with NAZUKE PON > About Japanese Names > Search For Japanese Names > Gennai Boy Name Meaning, Kanji Variations.