'Should' preserves the silent 'l' linking it to 'shall' — from Old English 'sculan' (to owe).
Used to indicate obligation, duty, or correctness; also used to indicate what is probable.
From Old English 'sceolde,' the past tense of 'sculan' (to owe, to be obligated), from Proto-Germanic *skulaną (to owe, to be obliged), from PIE *skel- (to owe, to be under obligation). The semantic journey from debt to moral duty is one of the most important in English grammar: what began as a concrete financial obligation ('I owe') became the language's primary marker of moral and epistemic obligation ('I should'). The silent 'l' in modern 'should' is etymological, preserving the connection to 'shall,' but it has been unpronounced since the 15th century. Old English 'sculan' carried the full
The silent 'l' in 'should' is not a spelling error — it preserves the word's kinship with 'shall,' of which 'should' is historically the past tense. The same pattern explains the silent 'l' in 'would' (past of 'will') and 'could' (past of 'can,' though 'could' added its 'l' by analogy — it was 'coude' in Middle English). In Old Norse, 'Skuld' was one of the three Norns (fates