In Mandarin Chinese, 万 (Pinyin: wàn 🔊) is a word for “ten thousand”. It is often used figuratively, in a sense “numerous”, “countless”, “very”, “extremely”, “absolutely”, “all”, “eternity” etc. 万水千山 (wàn shuǐ qiān shān), “ten thousand rivers, a thousand mountains” is a popular idiom for the long journey.
万 is a simplified form of the traditional hanzi 萬 which originally meant “scorpion”. There is a great variety of historical forms of this latter character. However, 万 and 萬 are not similar at all. According to Wiktionary, 万 is
a simplification of the Buddhist symbol 卍 introduced when Buddhism came to China. 卍 was given the same pronunciation as 萬 meaning 萬德 (many virtues); so, 卍 came to be used as a simplified form of 萬. 万 is simply a scribal form (script) of 卍. The meaning ten thousand for 万 is a borrowing.The modern character 万 does look more like a combination of Latin letters T and J than a left-handed swastika. Incidentally, “T.J.” is a nickname for Tijuana 🔊 — can you hear wàn there?