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SB 3.20.21

devas tān āha saṁvigno
 mā māṁ jakṣata rakṣata
aho me yakṣa-rakṣāṁsi
 prajā yūyaṁ babhūvitha
Synonyms: 
devaḥ — Lord Brahmā; tān — to them; āha — said; saṁvignaḥ — being anxious; — do not; mām — me; jakṣata — eat; rakṣata — protect; aho — oh; me — my; yakṣa-rakṣāṁsi — O Yakṣas and Rākṣasas; prajāḥ — sons; yūyam — you; babhūvitha — were born.
Translation: 
Brahmā, the head of the demigods, full of anxiety, asked them, “Do not eat me, but protect me. You are born from me and have become my sons. Therefore you are Yakṣas and Rākṣasas.”
Purport: 

The demons who were born from the body of Brahmā were called Yakṣas and Rākṣasas because some of them cried that Brahmā should be eaten and the others cried that he should not be protected. The ones who said that he should be eaten were called Yakṣas, and the ones who said that he should not be protected became Rākṣasas, man-eaters. The two, Yakṣas and Rākṣasas, are the original creation by Brahmā and are represented even until today in the uncivilized men who are scattered all over the universe. They are born of the mode of ignorance, and therefore, because of their behavior, they are called Rākṣasas, or man-eaters.