ETYM Latin assiduus, from assidere to sit near or close; ad + sedęre to sit. Related to Sit.
Marked by care and persistent effort; SYN. sedulous.

ETYM French diligent, Latin diligens, -entis, p. pr. of diligere, dilectum, to esteem highly, prefer; di- = dis- + legere to choose. Related to Legend.
1. Characterized by care and perseverence in carrying out tasks.
2. Quietly and steadily persevering especially in detail or exactness; SYN. persevering.

Careful in doing; diligent; faithful; attentive.
Taking pains; expending, showing, or involving diligent care and effort

ETYM Latin sedulus, perhaps from sedere to sit, and so akin to Eng. sit.
Diligent in one's activities; assiduous.
Taking great care; assiduous.