一切經音義 10.354

10.354

唅（何甘反短聲自下單書一字者皆是真言但取其聲以響梵字不求字義也）。

Hāṃ (唅: the fanqie hé + gān [何甘], short tone. From here on, those written as a single character are all mantras; only their phonetic value is taken to approximate the Sanskrit syllables, without seeking the character's lexical meaning).