Not able to add pool-member by name using curl command

As Stanislas indicates, you need to supply the address field if naming the node, however, as you are adding a pool member and not the node itself here, this curl statement should work for you:

curl -k -u admin:admin -X POST -d '{"name":"NodeTT:80","address":"10.10.10.10"}' -H "Content-Type: application/json" https://x.x.x.x/mgmt/tm/ltm/pool/BIGIQPOOL/members/

For my system, I slightly modified for a locally defined pool:

request
curl -k -u admin:admin -X POST -d '{"name":"NodeTT:80","address":"10.10.10.10"}' -H "Content-Type: application/json" https://172.16.44.128/mgmt/tm/ltm/pool/testpool/members

returned data 
{"kind":"tm:ltm:pool:members:membersstate","name":"NodeTT:80","fullPath":"NodeTT:80","generation":229,"selfLink":"https://localhost/mgmt/tm/ltm/pool/testpool/members/NodeTT:80?ver=11.6.0"}