My friend said sucking my breasts made him feel safe?

I have this male friend and he enjoys resting his head on my breasts and the other day helped himself to a suckle. We discussed it later on on Facebook and apparently he enjoyed it because it made him feel safe. What does he mean by this?
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Update: apparently he forgets about everything for a while when he is suckling. Like, stressors
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Oh, also might be worth mentioning that I told him off for swearing and he jokingly called me Mum 😂
My friend said sucking my breasts made him feel safe?
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