"Baptists".. people who stressed the importance of baptism (whole body immersion in water).. the nickname stayed as is, and the denomination came to be called "Baptists".
(The label "Christian" also came to be in the same way, people who repeatedly used the name of "Christ" came to called "those associated with or belonging to Christ" namely "Christians".)
In our church when people come to believe in and serve the one and only true God, to believe in Christ as the one who alone can save them, they are baptized and join the church. Jesus set the example in that He himself was baptized by John the Baptist in the river Jordan.
The word baptize comes from the Greek word "baptizó" which means to immerse in water. In the Catholic Church and part of the Protestant church (Anglicans, Lutherans, Presbyterians and Methodists) they sprinkle water on the head three times. However from the time of "Anabaptists" (one who baptizes again) in the 16th Century who desiring to faithfully follow the biblical description as far as possible, practiced full body immersion in water.
Furthermore the Baptist church does not practice infant baptism (baptism at the request of the parents), rather the individual is baptized when they personally believe in Christ as the only one who can save them and testify to (explain) this.
However for people that cannot be baptized by full water immersion for reasons such as being hospitalized, bedridden or for health reasons, baptism by sprinkling may be used (For it is by our faith that we are put right with God; it is by our confession that we are saved. Romans 10:10 TEV).
Other features include the separation of church and state, individual church doctrine (respecting each churches independence), the doctrine of universal priesthood (there are no classes, rather all believers are priests) and each church has a unique role to play in the community in which it is located.
In Japan there are more than 300 churches nationwide that are affiliated with the Japan Baptist Convention. Furthermore other affiliated organizations include educational institutions such as Seinan Gakuin University in Fukuoka, Seinan Jo (womans) Gakuin University in Kitakyushu, medical faculties such as the Baptist school of nursing in Kyoto and social welfare faculties such as the center for severely mentally and physically handicapped in Hisayama Fukuoka. The Baptist church seeks to serve God by helping people with education, medical care and welfare services as well as providing traditional church based ministry.
The Baptist family includes the Baptist association of Japan, the Okinawa Baptist convention and other Baptist churches around the world who work together totaling more than four million members worldwide.
Furthermore as brothers and sisters in Christ we work in cooperation with other denominations and associations.