The phrase the awkward age denotes the adolescence, when one is no longer a child but not yet properly grown up, a time of life characterised by physical and emotional changes.

The earliest instance of this phrase that I have found is from a portrait of Joseph Grimaldi (1778-1837), English actor, comedian and dancer, published in the North Wales Chronicle (Gwynedd, Wales) of Tuesday 7^th February 1832:

All great artists have devoted themselves very early in life to that in which they afterwards excelled. Mozart¹ composed in his infancy; Gainsborough² and Opie³ painted as soon as they could walk; Pope⁴ poetised in boyhood; and Joe Grimaldi came upon the stage when only two years old, making his debut in a pantomime called Robinson Crusoe, on 28th Dec. 1781. At Drury-lane Theatre Master Joseph did, from thenceforth, enact Cupids, zephyrs, fairies, fiends, &c. &c. but at length reached that awkward age, when like Master Daw⁵, he was—
For cupidons and fairies much too old,
For Calibans and devils much too boyish.

¹ Johann Chrysostom Wolfgang Amadeus Mozart (1756-91), Austrian composer

² Thomas Gainsborough (1727-88), English painter

³ John Opie (1761-1807), English painter

⁴ Alexander Pope (1688-1744), English poet

⁵ an allusion to the following lines from Low ambition; or, The life and death of Mr. Daw, published in Poetical Vagaries (London, 1812), by George Colman ‘the Younger’ (1762-1836), English author:

When Master Daw full fourteen years had told,
He grew, as it is term’d, hobbedyhoy-ish;
For Cupidons, and Fairies, much too old,
For Calibans, and Devils, much too boyish.

On 10^th July 1926, The Graphic (London) published Frocks for the Awkward Age: The “Sub-Deb” and her Special Needs, in which its Paris correspondent, Ethelyn Middleton, explained that the Maison Worth, “a famous dressmaking establishment” in Paris, “had opened a special department for the “sub-deb,” that is the girl from sixteen to eighteen”; she gave the following definition of the awkward age:

The sub-deb is in what we sometimes brutally call the “awkward age,” a period when the figure is not quite right for the sophisticated youthfulness of the older sister or matron and too mature for “little girl” models.

The following costume is one of the Worth models:

An early winter costume of checked blue and grey with pale blue crêpe de Chine blouse. The coat has collar and cuffs of grey fur.

The phrase the awkward age translates in French as l’âge ingrat, the thankless age. The adjective ingrat (feminine ingrate) means, literally, ungrateful; it also means, by extension:
– of a task, a subject matter, etc.: unrewarding, arid;
– of a soil: poor, infertile;
– of a face: unprepossessing, unattractive.

A synonym of l’âge ingrat is l’âge bête; as an adjective, bête means stupid, silly.