A four-character set phrase combining 只身 (zhīshēn, 'a single body / alone') and 一人 (one person) for emphasis. Carries a slightly literary, poignant tone - fits stories of migration, hardship, or quiet resolve.
mistakes
Don't confuse 只 (zhī, 'single') here with 只 (zhǐ, 'only'). The 'single body' reading takes the first tone - same as in 只身前往 (zhīshēn qiánwǎng, to go alone).
