[{"names":["name1,name2","name2,name3","name4,name1,name3"]},{"names":["name0,name2","name2,name3","name4,name1,name3"]}]

db.collection.aggregate([{$project:{names:{$reduce:{input:"$names",initialValue:[],in:{$setUnion:[{$split:["$$this",","]},"$$value"]}}}}},{$unwind:"$names"},{$group:{_id:null,names:{$addToSet:"$names"}}}])