Definition from Wiktionary, the free dictionary
dotard (plural dotards)
- An old person with impaired intellect; one in his or her dotage.
- 14th C., Geoffrey Chaucer, The Canterbury Tales, "The Wife of Bath's Prologue," lines 285-92, 
- Thou seist, that oxen, asses, hors, and houndes, / They been assayed at diverse stoundes; / Bacins, lavours, er that men hem bye, / Spones and stoles, and al swich housbondrye, / And so been pottes, clothes, and array; / But folk of wyves maken noon assay / Til they be wedded; olde dotard shrewe! / And than, seistow, we wol oure vices shewe.
- 1590, Edmund Spenser, The Faerie Queene, Book II, Canto Three, Stanza 16, The Faerie Queene, Book Two, edited by Erik Gray, Hackett, 2006, p. 44,
- "Dotard," (said he) "let be thy deepe advise; / Seemes that through many yeares thy wits thee faile, / And that weake eld hath left thee nothing wise, / Else never should thy judgement be so frayle, / To measure manhood by the sword or mayle.
- c. 1598, William Shakespeare, Much Ado about Nothing, Act V, Scene 1, 
- I speak not like a dotard nor a fool, / As under privilege of age to brag / What I have done being young or what would do / Were I not old.
- 1792, Mary Wollstonecraft, A Vindication of the Rights of Woman, Chapter 2, 
- The man who had some virtue whilst he was struggling for a crown, often becomes a voluptuous tyrant when it graces his brow; and, when the lover is not lost in the husband, the dotard a prey to childish caprices, and fond jealousies, neglects the serious duties of life, and the caresses which should excite confidence in his children are lavished on the overgrown child, his wife.
- 1835, William Wordsworth, "The Pass of Kirkstone" in A Guide through the District of the Lakes, 
- Lawns, houses, chattels, groves, and fields, / All that the fertile valley shields; / Wages of folly--baits of crime, / Of life's uneasy game the stake, / Playthings that keep the eyes awake / Of drowsy, dotard Time;—
- 1867, W. S. Gilbert, "The Precocious Baby," The 'Bab' Ballads, Complete Edition, Philadelphia: David McKay, no date, p. 73, 
- He early determined to marry and wive, / For better or worse / With his elderly nurse, / Which the poor little boy didn't live to contrive: / His health didn't thrive— / No longer alive, / He died an enfeebled old dotard at five!
- 14th C., Geoffrey Chaucer, The Canterbury Tales, "The Wife of Bath's Prologue," lines 285-92,