At the heart of deserve lies an old bargain: serve well, and you have earned what comes to you. Latin dēservīre intensified servīre (to serve) with the prefix dē-, creating a verb that meant 'to serve zealously' or 'to devote oneself completely.' The shift from devoted service to earned entitlement happened gradually in Vulgar Latin and early Romance — the logic being that thorough service creates a claim on reward. Old French deservir carried both the serving and the meriting senses when English borrowed it in the thirteenth century. English then did something the original Latin did not anticipate: it made deserve morally neutral. In Latin, dēservīre implied meritorious action. In English, deserve governs punishment as easily as praise. A criminal deserves imprisonment; a hero deserves recognition. This flexibility made the word indispensable to English moral reasoning. Curiously, modern French dropped deservir in favour of mériter (from Latin meritum), meaning French returned to a different Latin root for the same concept. The English noun 'desert' in 'just deserts' preserves the Old French connection — though most speakers now confuse it with the Sahara.