In a way that continues firmly despite difficulty or opposition; in a steady, determined manner.
From Latin 'persistere' (per- 'through' plus sistere 'to stand or cause to stand'). The word literally means 'to stand through' and entered English in the 16th century.
The root 'sistere' meaning 'to stand' shows up in dozens of English words—sister, resist, consist—which means persistence is literally about 'standing through' something, a metaphor buried in the word itself.
Complete word intelligence in one call. Free tier — 50 lookups/day.