Song reading; sō-on
Technical term in Japanese linguistics for the on reading of a kanji based on Song dynasty and later Chinese, especially common in Zen Buddhist vocabulary. Compare 唐音 (とうおん).
The sō-on reading of 行 in 行灯 is 'an'.
Tang-Song reading; tōsō-on
Compound of 宋 (そう, 'Song dynasty') and 音 (おん, 'sound; reading'). The term refers to Sino-Japanese readings that entered Japan during or after the Song dynasty.