井底之蛙 (Jǐng Dǐ Zhī Wā) literally means “well bottom’s frog” or “a frog in a well”. This Chinese Chengyu (成语) is used in a derogatory manner (see usage examples below) to describe someone who is ignorant or has a narrow worldview. A related 成语 is 坐井观天 (Zuò Jǐng Guān Tiān)
There is a story behind this four word idiom and the following is one of its variations:
There was once a frog who lived in a well and had never seen the outside world. One day, a turtle came to the well from the ocean. The frog saw the turtle and spoke to it, boasting about his well and inviting the turtle to come inside. However, the turtle was too large to fit into the well so he invited the frog to come out instead. When the frog stepped out of his well, he was amazed at the outside world and also ashamed that he had thought so highly of his well.
井 stands for well
底 means bottom (as in the bottom of something)
之 in this context acts like an apostrophe ‘s’
蛙 comes from 青蛙 (qīng wā) which means frog
Tā yīdiǎn jiànshì dōu méiyǒu, zhēnshi gè jǐngdǐzhīwā!
He doesn’t know anything at all, what a frog in a well!