Pillion

He afterwards remembered to the hour of his death, that when the hand of his sister, by which she supported herself on the pillion behind him, touched his own, it felt as wet and cold as sepulchral marble.

Source: tatoeba (7760820)

On my ancestor's donkey, I ride pillion.

Source: tatoeba (12675743)

It was all the greater triumph to Miss Nancy Lammeter's beauty that she looked thoroughly bewitching in that costume, as, seated on the pillion behind her tall, erect father, she held one arm round him, and looked down, with open-eyed anxiety, at the treacherous snow-covered pools and puddles, which sent up formidable splashings of mud under the stamp of Dobbin's foot.

Source: wiktionary

When he had gazed at the stars sufficiently as they shone over his mistress's window, and put her candle to bed, re repaired to his own dormitory, and there, no doubt, thought of his Maria andhis horse with youthful satisfaction, and how sweet it would be to have one pillioned on the other, and to make the tour of all the island on such an animal with such a pair of white arms round his waist.

Source: wiktionary