成唯識論述記 5.196

5.196

述曰：通名心識，非此相關。由此性、相二義，兼解所立名意所由，能審思量各自所取名末那故。

The Commentary states: The general designation 'cittam' or 'vijñānam' is not relevant here. Through these two meanings of nature and mark, it also explains the reason for establishing the name 'manas', because it constantly deliberates upon its respective grasped object, and is thus called 'manas'.