Haigo (a pen name of a haiku poet) (俳号)
Tosei is the first Haigo of Basho MATSUO. This Haigo is thought to have come from a family name on the mother's side of Momochi in Uwajima in the Iyo region. This 'Momochi' is a blood relative of the Momochi family that controls ninja, which is one of the grounds for the temporarily popular legend that Basho was ninja. The Haigo named 'Basho' comes from the fact that his pupil planted a Japanese banana plant (Basho), which was rare at the time, in a hermitage of Fukagawa, and Basho loved it. Basho sometimes used 'Bashoan Tosei' as his Haigo in his later years. Thus, it cannot be said that Basho simply changed his Haigo from Tosei to Basho.
Basho denotes his Haigo as 'Hasewo.'
In the case of Kabuki
Many Kabuki actors enjoyed furyu including haiku as part of the education in the Edo period, and Haimyo originated as an item for the Kabuki actors. As this cultural fashion was generalized to Kabuki actors, the item branched into Haimyo (a pen name of the haiku poet), which later developed into a name used by current actors. Haimyo has been used as a nickname when calling an actor on a stage. In the late Edo period, actors other than the chief Kabuki actors certainly had Haimyo in addition to a family stage name and other stage names whether or not he wrote haiku. Thereafter, Haimyo sometimes branched independently into one of the successions of a family name. For example, Baiko ONOE and Shoroku ONOE as a group of Kikugoro ONOE, Shikan NAKAMURA and Baigyoku NAKAMURA as a group of Utaemon NAKAMURA, and Gado KATAOKA, Gato KATAOKA, and Roen KATAOKA as a group of Nizaemon KATAOKA are successions of a family name derived from Haimyo. Moreover, the second-generation Ennosuke ICHIKAWA used by the first-generation Enno ICHIKAWA, and the first-generation Hakuo used by the eighth-generation Koshiro MATSUMOTO have branched into successions of the family name as inkyomei (name after retirement).
An excerpt for actors (lines of the role excerpted from the scripts) has only the name of the role and Haimyo on its cover. The stage name of the actor such as "so-and-so ICHIKAWA" is not often described on the cover. It is probably a preferential treatment for main actors. By the way, an actor who has inherited a succession of a family name derived from Haimyo also has another Haimyo.
For example, Baiko ONOE (the seventh generation) also had a Haigo called 'Sensha.'
In addition, in some haiku groups nowadays, Haigo in kukai (haiku gathering) is used to recognize regular members. Therefore, Haigo may serve as a handling name in the internet community that actively performs off-line meetings. On the other hand, some groups adopt a real name rather than Haigo after contributing a haiku in the bulletin.