Origins
The word 'obtain' entered English in the early fifteenth century from Old French 'obtenir,' descended from Latin 'obtinēre,' a compound verb meaning 'to hold onto,' 'to possess,' 'to gain,' or 'to prevail.' The Latin formation joins 'ob-' (a prefix meaning 'toward,' 'against,' or 'in the way of') with 'tenēre' (to hold), from PIE *ten- (to stretch). The literal image is of reaching toward something and taking hold of it.
Latin 'obtinēre' carried two distinct senses that both entered English. The first and more familiar is transitive: to get possession of something, to acquire, to secure. 'She obtained a degree,' 'he obtained permission,' 'they obtained the documents.' This is the sense most English speakers know. The second is intransitive and more formal: to prevail, to be in force, to hold good. 'The customs that obtained in medieval England,' 'the conditions obtaining at the time of the experiment.' This second sense preserves the Latin meaning of 'holding sway' or 'being in effect' and survives mainly in academic, legal, and formal writing.
The prefix 'ob-' in Latin had a range of meanings: 'toward,' 'against,' 'in the way of,' 'over,' and 'completely.' In 'obtinēre,' it functions as 'toward' — to hold toward oneself, to take into one's possession. This directional sense distinguishes 'obtain' from its siblings in the '-tain' family. 'Sustain' holds from below (supports). 'Maintain' holds by hand (keeps in condition). 'Retain' holds back (keeps from leaving). 'Detain' holds away (keeps from going). 'Contain' holds together (encloses). 'Attain' holds to (reaches). 'Obtain' holds toward (acquires).
Latin Roots
The '-tain' family is one of English's largest verb clusters from a single Latin source. All of them descend from 'tenēre' (to hold), and the semantic differentiation is entirely a function of the prefix. Understanding these prefixes unlocks the entire family: 'sub-' (under) gives 'sustain,' 'manu' (by hand) gives 'maintain,' 'per-' (through) gives 'pertain,' 'ad-' (to) gives 'attain,' 'con-' (together) gives 'contain,' 're-' (back) gives 'retain,' 'de-' (down/away) gives 'detain,' 'inter-' (among) gives 'entertain,' and 'ob-' (toward) gives 'obtain.'
In legal English, 'obtaining' carries specific technical weight. 'Obtaining by deception' or 'obtaining by false pretenses' are criminal offenses in many jurisdictions. The legal usage emphasizes that 'obtaining' involves active effort — one does not passively obtain; one reaches for something and takes hold of it. This active quality distinguishes 'obtain' from 'receive' (which can be passive) and connects it to its Latin etymology of grasping toward.
The formal intransitive sense ('the conditions that obtain') deserves attention because it reveals a layer of meaning that most modern speakers have forgotten. When we say 'those conditions obtained,' we mean they 'held' — they were in force, they prevailed. This is 'tenēre' in its purest sense: to hold, to hold firm, to continue to hold. The word's journey from 'to hold toward oneself' (to acquire) to 'to hold firm' (to prevail) shows how a single Latin verb could spin out multiple English meanings depending on which aspect of 'holding' was emphasized.