Brewer’s Dictionary of Phrase & Fable
LO AND BEHOLD: Would you believe; just imagine. A phrase introducing a surprising or unexpected fact. ‘Lo’ is related to ‘look.’ The tautologous phrase is not as old as it seems, and apparently dates from the 19th century.
Facts on File Encyclopedia of Word and Phrase Origins
LO AND BEHOLD: What a surprise! Can you believe it. The very old word ‘lo,’ which means ‘look’ or ‘see,’ today survives only in this tautological imperative, which dates from the mid-19th century and is nearly always used lightly. As Edward Bulwer-Lytton wrote (‘Night and Morning,’ cited by the OED []), “The fair bride was skipping down the middle . . . when lo and behold! the whiskered gentleman advanced.”
Oxford English Dictionary
LO []: [[ME; conflation of ‘lo,’ exclamation of surprise, grief, or joy, O! (Old English) ‘lo,’ shortened form of ‘loke’ (OLD ENGLISH ‘la’), imperative of ‘loken,’ to look)]] a) (obsolete) In early use, an interjection of vague meaning, corresponding approximately to the modern O! or Oh! b) Used to direct attention to the presence or approach of something, or to what is about to be said; = Look! See! Behold! Freq. in phrase ‘lo and behold’ (usually jocular).
Ken G – March 19, 2005<1480 “LO what a mariage was this as to the comparison of that other.”—‘The Chronicles of England’ (1482) by Caxton, ccliii., page 325>
<1758 “Lo! He comes with clouds descending.”—‘Hymns’ by C. Wesley>
<1807 “The prince drew near; where LO! an altar stood.”— ‘The Columbiad’ by J. Barlow, III.>
<1808 “Hartington . . . had just told us how hard he had worked all the morning . . . when, LO AND BEHOLD! M. Deshayes himself appeared.”—‘Letters’ in Correspondence (1912), June, I. page 20>
<1849 “What does he do, but, LO, AND BEHOLD you, he goes into a perfumer's shop.”—‘David Copperfield’ (1850) by Dickens, xxii. page 234>
<1930 “And then—LO AND BEHOLD—it was there all the time.”—‘Angel Pavement’ by J. B. Priestly, ii. page 60>
<1947 “You come in here and sprinkle the place with powder and spray perfume and cover the light-bulb with a paper lantern, and LO AND BEHOLD the place has turned into Egypt and you are the Queen of the Nile!”—‘Streetcar Named Desire’ by Tennessee William, x. 151>