'Obtain' is Latin for 'hold toward oneself' — from 'tenere' (to hold), the root of 'contain' and 'retain.'
To get, acquire, or secure something; (formal) to be prevalent or established.
From Old French obtenir, from Latin obtinēre (to hold, to keep possession of, to gain, to maintain), composed of ob- (toward, against, over) + tenēre (to hold, to keep). Tenēre derives from Proto-Indo-European *ten- (to stretch, to pull taut). The primary image is extending a hand toward something and closing it — holding it to oneself. The *ten- root is extraordinarily generative: it produced Latin tendere (to stretch), tensus (stretched), tenuis (thin, stretched thin), tenāx (holding firm), and the large English families built around tend, tension, tendon, tenacious, tenant
In formal or legal English, 'obtain' can mean 'to be prevalent' — as in 'the conditions that obtained at the time.' This preserves the original Latin sense of 'obtinēre,' which meant not only 'to get' but 'to hold sway,' 'to prevail.' Most speakers are unaware of this second, older meaning.