Sculptures occasionally appear in paintings, and while most are straightforward to read, there are two special breeds that deserve careful interpretation: herms and terms.
The Classical Greek herma, usually abbreviated to herm, is a sculpture consisting of a head and shoulders (sometimes also a torso) on a plain column usually of square section. They were normally placed at crossings and boundaries to ward off evil and protect those passing by.
In time, these herms acquired a phallus for good luck and fertility, and transformed into what the Romans called termini, or terms. Some of these became notorious for their association not with Terminus, god of boundary markers, but as celebrations of Priapus, god of fertility, and were often the bearer of male genitalia of alarming size.
Various deities appear on their column, sometimes even female.

In this joint painting by Rubens and Jan Brueghel the Elder of Nature Adorning the Three Graces from about 1615, three Graces are feting a term with about eight pairs of breasts, identified by Gombrich as the Ephesian Diana. Little is known of her cult, apart from her frequent representation as a herm with many swollen breasts as a symbol of fertility and fecundity.
It was Nicolas Poussin who was probably the most prolific painter of these sculptures, first in The Empire of Flora (also known as The Realm of Flora) from 1631.

This wonderful painting is set in a garden, with trees in the left background, a flower-laden system of pergolas, a large water feature, and dancing putti. Within this is a series of well-known characters, starting at the left with a herm representing Priapus.

More usually seen with an oversized and erect phallus, and abundant in Roman towns, Poussin opted for a touch of decorum in depicting the god of gardens and fertility, who was an inevitable associate of spring with its flowers. His phallus is also wreathed in greenery.

Poussin’s Bacchanalian Revel before a Term, painted a year or two later in 1632-33, features a rather more explicit term being feted and adorned by dancing maenads and fauns.

Poussin’s The Triumph of Pan (1636) is even more unbridled in its revelry, with a red-faced term at the back seemingly brought to life by the caress of the maenad in blue.
Herms and terms then led a reclusive life, making occasional appearances in later paintings, until they enjoyed something of a revival in the portraits of noble ladies painted by Sir Joshua Reynolds in the late eighteenth century.

Reynolds’ Portrait of Lady Elizabeth Keppel (1739-1768) from 1761 is busy adorning a term of Hymen with garlands, and has turned to her servant, who seems to have been occupupied making those floral tributes. This term is more traditional, with its square-section column, and it has arms bearing a long bridal torch. Its more troublesome crotch area has been carefully blocked from view.
Lady Keppel was unmarried at the time, and is shown wearing her bridesmaid’s dress from the recent marriage of King George III to Queen Charlotte. Her offering to Hymen seems to have done the trick, as she married the Marquess of Tavistock three years later.

Reynolds’ group portrait of the Montgomery Sisters bears the formal title of Three Ladies Adorning a Term of Hymen, and was painted in 1773. These three young ladies are engaged in the nugatory ‘work’ of making floral garlands for the term behind them.
While this term doesn’t have a classical base with a square section, the garland cunningly passes in front of the area of its crotch. The title, though, tells us that this term was not Priapus, but Hymen, the far more respectable ancient Greek god of marriage ceremonies. Reynolds has once again artfully steered us away from danger, and declared these three ladies’ interests in marriage.
Reading some paintings is just a matter of coming to terms with them.