ラテン語のtandem, last, exactly, duration, tam, hence, PIE*to, 指示代名詞の語源、the, thatと同じ語源、-dem, 指示副詞の接尾辞から。後者は、（2頭の馬が並んでいるのではなく）前と後ろに1頭ずつ、計2頭の馬が引く馬車を指すユーモラスな表現として使われ、後に前と後ろに1台ずつ、計2台の座席がある自転車を指す表現としても使われる。
英語の語源
tandem
tandem: [18] Latin tandem meant ‘eventually, at length’. Its use for ‘acting conjointly’ arose from an 18th-century play on words, in which ‘at length’ was jocularly interpreted as ‘lengthwise, in a straight line’, and the word was applied to a ‘carriage drawn by two horses one behind the other in a straight line’. In the 1880s it was transferred to a ‘bicycle with two seats, one behind the other’. Its more general modern use, for ‘acting together’, dates from the early 20th century.
tandem (n.)
1785, "carriage pulled by horses harnessed one behind the other" (instead of side-by-side), jocular use of Latin tandem "at length (of time), at last, so much," from tam "so" (from PIE *tam-, adverbial form of demonstrative pronoun root *-to-; see -th (1)) + demonstrative suffix -dem. "Probably first in university use" [Century Dictionary]. Transferred by 1884 to bicycles with two seats. In English as an adverb from 1795; as an adjective from 1801.
例文
1. He is working in tandem with officials of the Serious Fraud Office.
彼は詐欺事件の事務所の役人に協力して働いている。
2.Malcolm 's contract will run in tandem with his existing one.
マルコムの契約は、彼の手元にある契約と同時に有効になります。
3.The TANDEM welding is an ideal technology for the welding of panel in shipyard.
TANDEM 溶接プロセスは、造船所の合板溶接に理想的な溶接プロセスである。
4.He and his wife run the business in tandem ，ie as partners.
彼は妻と共同でこのビジネスを経営している。
5.Show that parallered branches and tandem branches may be replaced by equivalent graphs as shown below.