Sotoba is the Japanese transliteration of the Sanskrit word "stupa." It refers to the tower that originated in India. It diffused to Southeast Asian nations was well as to South Asian nations such as India, Pakistan and Nepal. The stupa that still exists in today's India is the well-known Sanchi Stupa, which was built in the third century by King Ashoka.
Originally, a stupa in India meant the mound where Busshari (the ashes of Shakyamuni (the founder of Buddhism)) were buried after his remains were cremated. Initially, a tower was built at the spot of Nirvana (Shakyamuni's birthplace) in honor of Shakyamuni. Subsequently, Buddhism diffused to other countries, and in the areas of fervent belief stupas were built to honor the Busshari. The stupa later became the building in which the ashes of a temple priest were placed after he or she died.
Stupa's diffusion to China
When the stupa diffused to China under the Han Dynasty, it was combined with the local architectural style and became the Chinese pagoda. The sorin (metal pinnacle) atop the Chinese pagoda was modeled after the stupa. Under the Yuan Dynasty, Buddhism became prosperous again, so many pagodas were constructed throughout China. This pagoda is called Fukubachi-shiki to (pagoda with a small, inverted bowl-like fixture placed on it), or Busshari to (pagoda to honor the ashes of Shakyamuni).
Stupa's diffusion to Japan
In Japan, sotoba is abbreviated as 'toba' and has the meaning of pagoda. However, it generally means a pagoda-shaped wooden tablet set up by the tomb, on which phrases from a sutra or the like are written for the repose of the soul of the deceased. The tablet is a simplified substitute for a pagoda, and it symbolizes godai (the five universal elements of earth, water, fire, wind and sky), just as gorinto (a kind of stupa composed of five different shapes of stones stacked atop one another) does. Sotoba, as derived from this tablet, occasionally refers to any of the traffic signs or the direction signs set up on roads in Japan, showing the road number or its common name.