Definition of "ado"

Antonio:In sooth, I know not why I am so sad.It wearies me; you say it wearies you;But how I caught it, found it, or came by it,What stuff 'tis made of, whereof it is born,I am to learn;And such a wantwit sadness makes of me,That I have much ado to know myself.

c. 1596–1598 (date written), William Shakespeare, “The Merchant of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene i]

Probably a crab would be filled with a sense of personal outrage if it could hear us class it without ado or apology as a crustacean, and thus dispose of it. “I am no such thing,” it would say; “I am myself, myself alone.”

1902, William James, The Varieties of Religious Experience