sedulous
Of a person: diligent in application or pursuit; constant and persevering in business or in endeavours to effect a goal; steadily industrious.
Since firſt this Subject for Heroic Song / Pleaſ'd me long chooſing, and beginning late; / Not ſedulous by Nature to indite / Warrs, hitherto the onely Argument / Heroic deem'd, [...]
Of an activity: carried out with diligence.
Now as there are many great wits to be condemned, who have neglected the increment of Arts, and the ſedulous purſuit of knowledge; ſo are there not a few very much to be pittied, whoſe induſtry being not attended with naturall parts, they have ſweat to little purpoſe, and rolled the ſtone in vain.
Where it comes from
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).
Adapted from the Wiktionary entry sedulous (CC BY-SA 4.0).