sedulous

Etymology

From Latin sēdulus (“diligent, industrious, sedulous; solicitous; unremitting; zealous”) + English -ous. Sēdulus is probably derived from sēdulō (“diligently; carefully; purposely; zealously”) (possibly from sē- (prefix meaning ‘without’) + dolō (ablative singular of dolus (“deceit, deception; evil intent, malice”), ultimately from Proto-Indo-European *del- (“to count, reckon”))) + -us (suffix forming adjectives).