侥幸阿
[jiăo xìng ā]
'侥幸' literally stands for a stroke of luck, '侥幸阿' is somewhat closer to 'what a lucky shot,' which shows surprise or even disbelief when something fortunate happens. So, using it as a nickname might express a lighthearted and humorous attitude towards one's experiences and personality traits, especially good luck or positive coincidences happening around the person often enough for this impression to take shape and be recognized.