illiquid comes from in- ('not') + liquid, from Latin liquidus ('fluid, flowing'), from liquere ('to be fluid'). A financial coinage meaning 'not readily turned into cash'. Morphologically, the prefixed shape matters: the initial element belongs to the recorded formation and helps explain the modern form's surface analysis. In present English, the adjective sense is "not easily converted into cash; lacking ready money", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as liquid, liquidity, and liquidate, and in derivatives such as illiquidity. Its semantic neighborhood includes cash-poor, frozen, and unconvertible, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin liquidus and Latin liquere.