I knew him not =  I did not know him 是古英语的否定说法。

王尔德《夜莺与玫瑰》英文原文：

"Here at last is a true lover," said the Nightingale. "Night after night have I sung of him, though I knew him not: night after night have I told his story to the stars and now I see him. His hair is dark as the hyacinth-- blossom, and his lips are red as the rose of his desire; but passion has made his face like pale ivory, and sorrow has set her seal upon his brow."

夜莺叹道, “真情人竟在这里。以前我虽不曾认识, 我却夜夜的歌唱他： 我夜夜将他的一桩桩事告诉星辰, 如今我见着他了。他的头发黑如风信子花, 嘴唇红比他所切盼的玫瑰, 但是挚情已使他脸色憔悴, 烦恼已在他眉端引着痕迹。”