At the root of the word 'Amateur' is the Latin 'Amat' meaning that an amateur is someone who does something purely for the love of it.

B. Baby, Backbone, Backer, Backup, Ball of fire, Baron, Beata (fem. ver. of:), Beatus, Beaut, Beauty, Beau ideal, Bee's Knees, Begetter, Being, Bel-esprit, Believer, Belle, Benchmark, Benefactor, Benefactress, Beneficiary, Benefit, Bestower, Bibliophile, Big cheese, Big enchilada, Big fish, Big gun, Big wheel, Bigwig, Biophile,Blessing, Bodyguard, Bon vivant, Boss, Booster, Brain, Brass, Brother, Bud, Buddy, Buff,Bundle of energy, Bundle of joy, Builder

C. Campaigner, Captain, Carer, Caretaker, Cartophile, Catalyst, Cat's meow, Cause, Cavalier, Celebrant, Celebrator, Center of attention, CEO, CFO, Chair, Chairperson, Chamberlain, Champ, Champion, Chaperon, Charmer, Cherub, Cherisher, Chief, Chieftan, Child, Chum, Cinephile,Clerisy,Climber, Coadjutant, Coadjutor, Cognoscente, Cognoscenti, Cohort, Coiner, Collaborator, Colleague, Collector, Comforter, Commander, Companion, Compeller, Complement, Composer, Comrade, Concert pianist, Concierge, Conductor, Confederate, Conferrer, Confidant, Confrere, Connoisseur, Conservator, Consoler, Consul, Consultant, Contributor, Controller, Convive, Cooperator, Corker, Cornerstone, Cosmocrat, Cosmopolitan/Cosmopolite, Councillor, Counsel, Counselor, Counsellor, Count, Co-worker, Crackerjack, Craftsperson, Creator, Credit, Crew, Cub, Curator, Custodian, Cynosure

D. Dad, Dancer, Darling, Daughter, Dean, Dear, Defender, Deipnosophist,Demophile,Designer, Devisee, Devisor, Devotee, Digerati,Dilly, Director, Disciple, Discophile, Discoverer, Distributor, Doer, Doll, Donee, Donor, Doter (rare: doater), Doozy, Doula, Doyen/Doyenne, Dream, Dreamboat, Duke, Dynamo