Why is a legal action called a suit?

The law has many strange and esoteric terms.  Have you ever wondered where the term suit, as it refers to a legal proceeding, came from?  Black’s Law Dictionary defines suit as “[a]ny proceeding by a party or parties against another in a court of law; case.”  It adds “lawsuit” and “suit at law” as synonyms.1  The use of the term suit originated in 14th century England, before there were organized court systems.  Disputes were settled in open-air communal meetings.2  The goal was not a reasoned decision, but an amicable settlement.  If that could not be achieved, the next resort was proof by oath, backed up by a physical challenge of some sort.
“In order to put the defendant to this hazard [physical challenge], the plaintiff was required to establish a prima facie case; and this was the purpose of his ‘suit’ (secta), the group of followers whom he had brought with him to back him up on oath. The suit had some affinity with witnesses, and they may have been subject to examination as to competence, but their testimony was only part of the interlocutory process and did not dispose of the matter.”3
“This sort of ‘witness,’ …, might have nothing to do with the trial; he belonged to the stage of the preliminary allegations, the pleading, where belonged profert (sic) of the deed upon which an action or a plea was grounded.” In time, the suit was absorbed into common-law procedure, mostly serving as transaction witnesses when written contracts were rare.5  Eventually, “they were not even produced, and only the formula in the pleadings was kept up.”6   Today, the allegations in a complaint filed to initiate a lawsuit serve the same function – of presenting a prima facie case – as the 14th century suit.  In the practice of adjudicating a motion to dismiss a lawsuit for failure to state a claim by taking the plaintiff’s allegations as true,7 we hear the echo of the medieval principle that the suit cannot be examined.

1. Black’s Law Dictionary (9th ed. 2009).
2. J.H. Baker, An Introduction to English Legal History 5 (3rd ed. 1990).
3. Id. (emphasis added).
4. James B. Thayer, The Older Modes of Trial, 5 Harv. L. Rev. 45, 48 (1891).
5. Baker at 362.
6. Thayer at 48.
7. “The question is whether, in the light most favorable to the plaintiff, and with every doubt resolved in his behalf, the complaint states any valid claim for relief.” Gentry v. Yonce, 522 S.E.2d 137, 139 (1999).