Rōmusha is a Japanese word meaning "an unskilled laborer who carries out temporary contruction work". In Japanese-occupied Indonesia, the words 'by force" and "hard physical work" were added to this definition.
On 10 July 1942, the Japanese army in Indonesia arranged the first transport of Javanese rōmusha to other territories in South East Asia.
Java became the primary source of forced laborers during the Japanese occupation of the Pacific. In total, between 200,000 and 300,000 rōmusha were sent from Java to other territories.
Forced labour on the Burma-Siam Death Railway has remained the most famous example of their use. The majority of the workers on the Death Railway were not the Allied POWs, but rōmusha from other Sout-East-Asian countries.
Quoted from: Takuma Melber, 'The Labour Recruitment of Local Inhabitants as Rōmusha in Japanese-Occupied South East Asia' in IRSH 61 (2016, Special Issue), pp 165-185.