What did Buddha mean by the words "tranquillising the bodily formation" in the Anapanasati Sutta?

> “Here a bhikkhu, gone to the forest or to the root of a tree or to an empty hut, sits down; having folded his legs crosswise, set his body erect, and established mindfulness in front of him, ever mindful he breathes in, mindful he breathes out. > > “Breathing in long, he understands: ‘I breathe in long’; or breathing out long, he understands: ‘I breathe out long.’ Breathing in short, he understands: ‘I breathe in short’; or breathing out short, he understands: ‘I breathe out short.’ He trains thus: ‘I shall breathe in experiencing the whole body of breath’; he trains thus: ‘I shall breathe out experiencing the whole body of breath.’ He trains thus: ‘I shall breathe in tranquillising the bodily formation’; he trains thus: ‘I shall breathe out tranquillising the bodily formation.’ This passage is translated with the same words in my native language, but I don't understand what does it mean. The other English translation translates this as "stilling the body’s motion". Does "tranquillising the bodily formation" means the same as "stilling the body’s motion"?